Process of recovering zinc from ores.



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To all whom it may come:

Be it known that we, Fumes: latter and James 01m Enron, citizens ofthe United States, residing at Anaconda, in the county of Deerlodge and State of Montana, have invented certain new and useful improvements in Processes of Recovering Zinc, from a simple treatment with such basic reagents as zinc oxid, lime, etc., will sufice not only to eliminate the iron, but to precipitate therewith a part at least of the arsemc and antiinony, probably in the form of ferric arsenate and antimonate.

In the practice of this method it has been found that in order to insure the substantially complete elimination of arsenic and antimony from such solutions, the ferric iron must he present therein in material ex cess of the proportion theoretically required for formation of the corresponding arsenates and antimonates, and in fact in larger proportion than is usually derived from a properly calcined ore under the usual leaching conditions. 0n the-other hand the presence of iron in solution seriously interferes with the proper recovery of zinc in the electrolytic cells.

According to the present invention this ditliculty is avoided by means of a cyclical operation wherein iron salts are introduced into the solution'at a stage following the electrolysis, and are removed therefrom, togather with the arsenic and antimony, at a stage preceding the next electrolysis. lln

this way the presence of sucient iron is insured during the purifying stage, while the practically iron-free electrol ll the a specification of letters Patent.

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metal in cells having insoluble anodes, whereby an exhausted or impoverished electrolyte containing free sulfuric or other acid 1s obtained, and is used for leaching fresh hatches of ore. According to one embodiment of our invention this acidisolution is permitted to flow, on its return from the electrolytic cells to the ore leaching tanks, over scrap iron or a soluble iron ore, whereby its iron content is brought to the proportion necessary for substantially complete re moval of any arsenic and antimony which may pass into solution in the leaching operation, or if desired a solution of an iron salt may be added directl to the acid solution flowing into the leaching system. During or after the leaching this iron must be brought completely into the ferric state by means of any suitable oxidizing agent, of which manganese dioxid is one of the most effective. The iron is then completely precipitated, preferably by zinc oxid or fine calcines, and the solution after further purification if required returns to the electrolytic cells, thereby completing the cycle.

Although a system of this kind is efi'ective for the removal of arsenic and antimony, ditficulty is sometimes experienced, owing to slow solution of metallic iron or iron ore in such dilute acid solutions as are used for leaching roasted zinc ores; and owing also to slow oxidation of the iron after it has been dissolved. It will be understood inv this connection that unless all of the iron is in the ferric state,- its complete removal is very dificult. We have found, however, that all of the above dificulties may be overcome by the following modification of the above described process. Scrap iron or iron ore is treated with an excess of sulfuric acid of suficient concentration (say to react rapidly therewith the action being preferably continued until the solution contains 5% or more of iron. Manganese dioxid, or an ore or other material containing manganese in a state of oxidation higher than the manganous state is then added to the hot acid solution, whereupon all of the iron is quickly brought to the ferric state. The resulting ferric solution, containing also manganous salts, is then added to each leach to furnish sucient iron for the can of are =11: d

lltih antimony as arsenate andantimonate. After the removal of the ferric iron the man ganous salts may be reoxidized in the electrolytic operation, and are thus available for reuse in a repetition of the process.

' We claim:

1. A cyclical process of recovering zinc from ores thereof containing arsenic or antimony, consisting in alternately leaching the ore with an acid solvent for zinc, and electrolytically precipitating zinc from the resultmg solution, introducin iron into the.

timony, consisting in alternately leaching the ore with an acid solvent for zinc, and electrolytically precipitating zinc from the resulting solution, introducing a ferric salt into the solution subsequent to the electrolysis and in proportion suflicient for the substantial elimination of arsenic and antimony, and removing the iron from the solution, together with the arsenic and antimony, by

precipitation prior to the succeeding electrolysis.

3. In a process of recovering zinc from ores thereof containing arsenic or antimony, the steps which consist in preparing a solution containing a ferric salt, and introducin the same into the leach in proportion su cient for the substantially complete elimination of arsenic and antimony.

4. In a process of recovering zinc from ores thereof containing arsenic or antimony, the steps which consist in preparing an acid solution containing a ferrous salt, oxidizing the same by means of a compound containing manganese in a state of oxidation higher than the manganous state, and introducing the resulting solution containing ferric and manganous compounds into the leach in proportion sufficient for the substantially complete elimination of arsenic and antlmony.

5. In a process of recovering zinc from ores thereof containing arsenic or antimony, the step which consists in introducing into the leach a solution containing ferric and manganous salts.

In testimony whereof, we aflix our signatures.

FREDERICK LAIST. JAMES ORR ELTON. 

